Sybase DBLink – Setting Up Between Two Databases

dblinksybase-sql-anywhere

I am having dificulty finding anything on the net on this subject.

I am tasked with creating a DBLink between two Sybase Databases. At the moment it's not yet clear if they will be on the same server or on seperate machines in the same network. What I do know is that they are both gonna run on the same Version of Sybase SQL Anywhere 12.

All I can find is how to creat a DBLink from Oracle or MSSQL to Sybase.

I can't seem to find anything about Sybase to Sybase.

I am sorry if my terminology is a little wonky, I am new to Sybase/ASA.

Best Answer

I think it's a terminology problem. SQLA has the concept of a Remote Server - which could be Oracle, MS SQL Server or another SQLA database. Once you have set up a Remote Server, then you can set up remote tables etc.

It doesn't make any difference to the way you use it whether the other SQLA database is on the same database engine, another engine on the same server or a completely different server. Don't forget that SQLA has no concept of a Master database, every database is autonomous.

There are a lot of details for v12.0.1 at this URL : http://dcx.sybase.com/index.html#1201/en/dbusage/ug-accessrd.html

In Sybase Central you will see an entry for Remote Servers in the object tree. The SQL commands are CREATE SERVER and CREATE EXISTING TABLE.

If you have problems it would be worth asking on the dedicated SQLA site: http://sqlanywhere-forum.sap.com/

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PostgreSQL: DBLink weird permission/connection error

Here is what I think is happening. I don't think it is a bug.

You have a view. That view is somewhat complex but it is a dynamically rewritten query.
The planner is pretty smart. It will ignore UNION clauses where the search criteria will not produce an output result.
You are not executing what you think you are. (EXPLAIN ANALYSE should show you this)

My recommendations:

Wrap the whole result set in a plpgsql function. Wrap that function in the view. OR
Use a WITH clause. I am less sure about this one. I think the with clause might result in running the whole thing consistently but not 100% sure, and it is not guaranteed in future versions. Therefore wrapping in a function is probably better.

I think what the planner is seeing is:

"Oh we don't need to execute the first and third portions of the view because they are not in the output! Let's skip and only run the second portion!" This is a feature, not a bug (and it is what allows table partitioning to be useful).

Limit Memory Usage for Sybase SQL Anywhere

Sybase's SQL Anywhere has startup parameters to control the min/max cache settings.

  -c  for the initial cache memory setting
  -ch for the maximum cache memory setting
  -ci for the minimum cache memory setting

If you set these appropriately it should constain the memory usage from the cache.

Here is a SQL Anywhere 12.0 page with those settings: http://dcx.sybase.com/1200/en/dbusage/limiting-using-perform.html

Best Answer

Related Solutions

PostgreSQL: DBLink weird permission/connection error

Limit Memory Usage for Sybase SQL Anywhere

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